A magnetron co-sputtering strategy of incorporating copper to enhance the electrocatalytic oxygen evolution performance of manganese

The development of efficient, earth-abundant, and cost-effective electrocatalysts for the oxygen evolution reaction (OER) is crucial for large-scale hydrogen production via water electrolysis. Inspired by the manganese cluster in Photosystem II, manganese-based materials are considered as promising OER candidates. However, their widespread application faces two major bottlenecks: poor electrical conductivity due to their intrinsic semiconducting nature, and poor stability caused by structural evolution or dissolution during catalysis. Herein, we propose a strategy of bimetallic alloying with copper (Cu) to simultaneously overcome these dual challenges. A series of Cusingle bondMn alloy thin films with tunable atomic ratios were prepared using a facile magnetron co-sputtering technique. This method not only fundamentally solves the conductivity issue by forming a metallic phase but, more importantly, the incorporation of Cu modulates the electronic structure of Mn. During the electrochemical OER process, the initial alloy undergoes in-situ surface reconstruction to form stable higher-valence manganese species (Mn3+/Mn4+), which serve as the actual catalytic active sites. This optimizes the adsorption energy of OER intermediates, in line with the predictions of the volcano plot theory, and reinforces the structural stability of the material. Electrochemical evaluations confirm the success of this strategy. The optimized Cu30Mn70 (at.%) alloy exhibits outstanding catalytic activity in 1.0 M KOH, requiring a low overpotential of only 325 mV to drive a current density of 10 mA cm-2 and demonstrating favorable reaction kinetics with a Tafel slope of 76.5 mV dec-1. It also demonstrates commendable stability. This overall performance surpasses most of the previously reported Mn-based oxide and composite catalysts. This work clearly demonstrates that simple metallic alloying is a powerful avenue for designing high-performance non-precious metal catalysts with synergistically enhanced activity and stability for efficient energy conversion.